In a variety of factories, buildings, etc., a water system including various heat exchangers, e.g., refrigerating machines, is installed, and an object to be cooled is cooled by contacting circulating water (cooling water) and the object to be cooled with each other through the heat exchanger. Recently, in a circulating water system, it has been prevalent to operate the system under a condition of holding the circulating water at a higher concentration for the purpose of saving water. Under such an operating condition, however, an ion component is concentrated with evaporation of the circulating water, thus resulting in a possibility that scale may precipitate and adhere to the interior of the refrigerating machine.
With scale adhering to the interior of the refrigerating machine, heat transfer to the circulating water from the object to be cooled is impeded. Such a situation may lead to an event that a condensation degree of the object to be cooled reduces and pressure rises in a condenser, or that the load of a compressor increases with a rise of temperature of the object to be cooled, thus causing high-pressure cutout (i.e., stop of the compressor at pressure in excess of a certain level). Furthermore, the adhesion of scale reduces the refrigeration capability of the refrigerating machine, thereby increasing power consumption and reducing energy efficiency. It is hence required to appropriately perform concentration management in the circulating water system, and to suppress the precipitation of scale.
Generally, various water treatment chemicals are added into the circulating water system to prevent or reduce the occurrence of scale, slime, and corrosion. For example, there is known a method of controlling the concentration of a water treatment chemical, which is present in circulating water, by measuring the concentration of an organic substance contained in the circulating water, and by determining an added amount of the water treatment chemical on the basis of a measured value (see Patent Literature 1). There is also known a method of performing concentration management in the circulating water system by setting a threshold for electrical conductivity of the circulating water, and by executing an operation of reducing a concentration factor (such as increasing a blowing rate or injecting makeup water) when the electrical conductivity exceeds the threshold.
Here, the electrical conductivity of the circulating water is given as a value obtained by adding an electrical conductivity, which is resulted from multiplying an electrical conductivity attributable to components dissolved in the makeup water, by a concentration factor, and an electrical conductivity attributable to the chemicals added to the relevant water system. In other words, an accurate concentration factor cannot be obtained through a simple calculation of just by dividing the electrical conductivity of the circulating water by the electrical conductivity of the makeup water.
Patent Literature 1: Japanese Patent Publication 2002-210454 A